Watering is often thought of as the easiest part of looking after houseplants, and it is at its core. However, more houseplants die from being watered wrongly than from anything else you could do to them. It isn’t that people don’t try; in fact, most of us water our plants often and with good intentions. The issue is “often” for many of us boils down to a set routine, and plants don’t use water in a way that fits a schedule. How much water a plant needs shifts all the time, depending on how much light it gets, the temperature, how humid it is, the size of the pot, the soil it’s in, the time of year, and how much the plant is growing. You really have to go by how the soil feels to water a plant successfully, rather than by what day it is.
Why Calendar-Based Watering Fails
During the middle of summer, a houseplant in a sunny south facing window can dry out its soil in just two days. That same plant in the same pot, but during the brief, dark days of December, will take a whole ten days to use up an equal amount of water. If you water both in summer and winter on a set schedule, like every Wednesday and Sunday, your plant will either get too much water all winter, or not enough in the summer, and perhaps a bit of both depending on the time of year. The biggest reason water needs change with the seasons is how strongly, and for how long, the sun shines. However, the temperature of the room, how much moisture is in the air (which falls a lot when houses are heated during the winter), and how the plant is growing all add to why a regular watering timetable doesn’t work.
The Finger Test: The Most Reliable Method
To figure out when your houseplant needs water, and do it in a way that will pretty much always work, just use your finger. Stick your finger into the soil about an inch or two, as far as your first knuckle goes. If the soil at that depth is dry, your plant is thirsty. But if it is still wet, don’t water it, and this is true no matter how long it’s been! Plants that like to be kept pretty damp all the time (things like ferns, calatheas and peace lilies) should be watered once the top half inch of soil feels dry. However, for plants that can take dry spells (succulents, cacti, snake plants, ZZ plants), you should hold off on watering until the soil is dry almost all the way down to the bottom of the container. Using this one method regularly will save nearly all houseplants from being either overwatered or not watered enough.
How to Water Thoroughly When It Is Time
If poking your finger in the soil says the plant needs water, give it a good soaking, don’t just use a little. Water should go onto the soil slowly until you get water coming out of the holes at the bottom of the pot. This makes sure all the roots get wet, and not only the surface of the soil. Lots of people water lightly and often, but this only gets the upper soil moist, and leaves the roots deeper down permanently dry. Because of that, the roots will grow up instead of down, and the plant will be weaker, needing water all the time. Once you have soaked the plant, get rid of any water that has collected in the tray underneath it within half an hour. You don’t want the roots to be sitting in water.
Adjusting for Pot Type, Soil Mix, and Season
Because terra cotta pots have lots of tiny holes, water goes through the sides and the soil gets dry more quickly than in plastic or ceramic pots. This means plants in terra cotta need you to look at them for water more often. Potting mixes based on peat will hold onto water for a longer time than those with a lot of perlite or bark, but if they get completely dry, they can get to a stage where they push water away. This happens fairly often in winter because you’re not watering as much. If you water and the water just flows down the inside of the pot instead of sinking into the soil, the soil is too dry to absorb it, and you’ll need to get the whole pot and set it in a bowl or container of water for fifteen to thirty minutes. The water will soak up into the soil from the bottom. Most indoor plants don’t grow much in the winter, and as a result, you should water them less – and a quick feel of the soil (the ‘finger test’) will show you the soil stays damp for much longer between waterings.
Key Takeaway
The best way to know when your houseplants are thirsty is to stick your finger in the soil, down about one or two inches. Unlike just going by the calendar, this actually works, because plants need different amounts of water all the time depending on how much light they get, the temperature and how actively they are growing. And when they do require water, really give them a good soaking; water until it runs out of the holes at the bottom of the pot. You should get rid of any water in the tray the pot sits in after around half an hour. This way of checking and then soaking is what stops the two things that are most likely to kill a houseplant: consistently too much water, or too little that doesn’t get to all the roots.
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